1. Field of the Invention
The present invention relates to a method, for separating paper and plastics in a wetted mixture of essentially paper and plastics sheeting pieces, using an upward stream of gas. The invention also relates to separating means for carrying out this method.
2. Description of the Prior Art
Usually a sifter used for separating paper and plastics pieces is a vertically arranged zig-zag duct in which the mixture is separated by an upward stream of gas. This separation is due to the factors which determine whether the pieces of the mixture fall or rise in the stream of gas. In the case of a mixture of pieces of paper and plastics sheeting it is particularly the difference in the density of the materials which is important in the separation process.
A process of this type is disclosed from Dutch Pat. No. 158.565. This patent describes how, before sifting, the mixture is wetted, so that the paper absorbs a quantity of moisture, thus magnifying the small difference between the density of paper and plastics when dry, to produce better separation.
However, in use of this process, it has been found that the difference in the density of the paper and the plastics after wetting is less than expected and that optimum separation of these materials is not obtained. It is believed that this is because the moisture increases the weight not only of the paper but also of the plastics, because a film of the liquid used to moisten the mixture forms on the pieces of plastics.
Two further items of prior art are discussed below.